public class Test1 {
     public static void main(String[] args) {
        /* String str = "helloworld" ;

         System.out.println(str.substring(5));

         System.out.println(str.substring(0, 5));
         String str = "  hello world  " ;

         System.out.println("["+str+"]");

         System.out.println("["+str.trim()+"]");*/
         String str = "  hello%$$%@#$%world 哈哈哈 " ;

         System.out.println(str.toUpperCase());

         System.out.println(str.toLowerCase());
     }
}
